When Australia became a Federation in 1901, the Senate was created with the intention of allowing each original state (NSW, Vic., Qld, WA, SA and Tas.) to be equally represented.
The electors in each state and territory elect a number of people to represent them in the Senate. Each state has an equal number of senators.
Initially, there were six senators elected from each state, giving a total of 36. There have been three increases in the size of the Senate since Federation. Legislation passed in 1948 increased the number from 36 to 60 (i.e. 10 per state), in 1974 from 60 to 64 when the ACT and the NT each gained two senators, and in 1983 from 64 to 76, i.e. 12 per state and two per territory. Changes took effect at the elections that followed.
Senators for each state are elected for six–year terms on a rotating basis, with half the senators retiring every three years(or facing a half–senate election). The terms of senators representing the ACT and the NT commence on the day of their election and expire at the close of the day immediately before the polling day for the next general election of members of the House of Representatives. The election of these senators is held at the same time as every general House of Representatives election.